| 摘要 |
PURPOSE:To obtain and set a loss of transmission to be given and then increase the service quality, by detecting the size and amount of delay of a circulating current of a connection route at the end of exchange and connection. CONSTITUTION:The test signal is decoded to a test signal within aural band by the decoder 22 through the reception digital filter 23 and furthermore turned into a echo current of the 2-/4-wire converting circuit 3 to pass through the circuit 3. This echo current is then coded by the coder 18 to be sent to the remote terminating station via the transmission digital filter 19, compounder circuit 20 and time-division switch 21. The test signal made a round of the remote terminating station reaches the digital loop current detection circuit 17 via the time-division switch 21, expander circuit 24 and drop inserter 14. Both the amount of return current and the amount of delay are measured at the circuit 17, and the loop current measuring device 15 processes these measurements to give a change to the filter coefficient of the transmission and reception digital filters 19 and 23 each. |
